1. Field of the Invention
The present invention relates to the technology that facilitates transient and still visual images in portable information processing systems such as a system consisting of a notebook-type personal computer and PC cards.
2. Description of the Related Art
A portable information processing apparatus such as a notebook-type personal computer usually has a built-in display monitor and PC card slots for expansion interfaces.
FIG. 8 shows a block diagram of a prior portable information processing apparatus. The prior portable information processing apparatus comprises a liquid crystal display 13, abbreviated to LCD hereafter, that displays images, a VRAM 11, called frame buffer memory hereafter, that stores image data, a synchronizing signal source 28 denoted by CLK that provides a synchronizing signal, a VGA controller 12 that converts the data stored in frame buffer memory 11 into video signals, called analog RGB signals hereafter, synchronized with the synchronizing signal provided by synchronizing signal source 28, an LCD controller 14 that controls LCD 13 based on the analog RGB signals output from VGA controller 12, PC card slots 18, 19 for installing PC cards 15, 16, and a PC card controller 17 that controls the installed PC cards 15, 16. VGA controller 12 and PC card controller 17 are connected to a system bus 23. A CPU 24, main memory 25, ROM 26, and input/output devices 27 including a key board and external storage devices are also connected to system bus 23.
Images are displayed by this information processing system as follows. Image data stored in frame buffer memory 11 is converted by VGA controller 12 into analog RGB signals synchronized with the synchronizing signal provided by synchronizing signal source 28, and the analog RGB signals are input to LCD controller 14. The analog RGB signals are converted by LCD controller 14 into a scanning signal and output into LCD 13, which displays images. Therefore, for a portable information processing apparatus to be able to display images, it is necessary to input a synchronizing signal and RGB signals to LCD controller 14. In the prior portable information processing apparatus, these signals are controlled through VGA controller 12.
As described above, prior portable information systems have no path between PC card slots 18, 19 and VGA controller 12 or LCD controller 14 for directly passing signals from one to the other. Therefore, image data provided by PC cards 15, 16 has to be processed by VGA controller 12 and LCD controller 14 through system bus 23. However, in order to realize this process, high-performance CPU 24, mass-storage main memory 25, and others are required to be practically almost impossible in a portable system. Therefore, application products that deal with transient visual images and hence require direct control over VGA controller 12 and LCD controller 14, such as TV tuners, TV telephones, video disks, have been difficult to make in the form of PC cards.
However, in the near future, it will become indispensable for a portable information system to have such functions as to receive TV programs, to exchange images, voice, and data over telephone lines, and to play back image data recorded on a video disk. Therefore, if notebook computers can easily handle visual images by installing PC cards capable of such functions, then everyone can easily use so-called multimedia in any place without large space.